Welded fluorescent lamp base pins



June 5, 1956 w. F. ALBRECHT WELDED FLUORESCENT LAMP BASE PINS Filed July1, 1953 5 Sheets-Sheet 1 Invent on Warren FT Albrecht, by [Aw/fr- K HisAttorney June 6 w. F. ALBRECHT WELDED FLUORESCENT LAMP BASE PINS 3Sheets-Sheet 2 Filed July 1, 1953 Inventor; Warren F Albrecht, by VMJ fl/f His Attorney June 5, 1956 w. F. ALBRECHT 2,749,528

WELDED FLUORESCENT LAMP BASE PINS Filed July 1, 1953 5 Sheets-Sheet 3Inventor; Warren F Albrecht,

His Attorney United States Patent O WELDED FLUORESCENT LAMP BASE PINSWarren F. Albrecht, Euclid, ()hio, assignor to General Electric Company,a corporation of New York Application July 1, 1953, Serial No. 365,429

4 Claims. (Cl. 339-145) This invention relates to the basing of electriclamps of the type using elongated hollow pins or prongs for contactterminals. More particularly, it relates to the connection of the leadwires to the base pins of the common fluorescent lamp having a bi-pinbase, by an electrically welded junction.

The object of the invention is to provide a new and improved weldedconnection between the lead wire and the tubular contact pin in electriclamps using pin type bases.

Another object of the invention is to provide a new and improvedconnection between the lead wire and the tubular pin of an electric lampbase, which connection is achieved by electric welding as a result ofwhich the outer end of the pin is closed by metal resulting from thefusing of the end of the pin and of the wire into a solid mass andwithout any addition of metal thereto from an ex traneous source.

In accordance with the invention, there is provided a welded connectionof the lead wire to the tip of a hollow tubular contact pin whichconnection completely seals the open end of the pin. The weldedconnection consists of intermingled and fused metal from a shortprojecting stub of the lead wire and from the tip of the pin. The pin isforeshortened slightly as a result of the weld, and the weld itself isachieved by a welding current having a drooping characteristic.Preferably, it is achieved by discharging a capacitor between the pinand a massive electrode which is brought into contact with theprojecting stub of the lead wire, the electrode being negative inpolarity in the circuit.

For further objects and advantages and for a better understanding of theinvention, attention is now directed to the following description andaccompanying drawings. The features of the invention believed to benovel will be more particularly pointed out in the appended claims.

in the drawings,

F i g. 1 is a sectional view of one end of a fluorescent lamp providedwith a bi-pin type base.

Figs. 2a to 2d illustrate diagrammatically the various steps followed inmaking a welded pin connection embodying the invention.

Figs. 3a and 3b are enlarged detail views, the former of a pin about tobe welded, and the latter of a welded pin connection embodying theinvention.

Figs. 4a and 4b are similar to Figs. 3a and 3b and illustrate a variantof the invention.

Referring to Fig. 1, there is shown in section an end of a fluorescentlamp 1 provided with a bi-pin base 2 of the type toward which theinvention is specifically directed. The lamp comprises a vitreous tube 3to which is united a mount 4 comprising a flare 5, the peripheralportion of which is united to the tube and a press 6 through which aresealed lead wires 7 for the support of a filamentary cathode 8. The base2 which caps the end of the lamp comprises a shallow metal shell or cup9 which is cemented at 11 to the end of the tube. The

cutters such as illustrated in Pig.

lead wires 7 are threaded through hollow tubular contact pins 12 whichare fastened to the end wall of the base shell 9 and insulatedtherefrom. Each pin 12 (seen more clearly in Fig. 3a) comprises agenerally cylindrical tubular shank or body 13 which is outwardlyexpanded at 14 into an annular ridge. This ridge seats on an outer fiberwasher 15 which fills a shallow well on the end wall of the base shell.The lower end of the pin is upset at 16 under an inner fiber washer 17whereby the pin is securely staked to the base shell, It will beobserved that the well in which the upper washer 15 is seated isprovided with a central perforation 18 considerably larger in size thanthe diameter of the pin whereby the pin is insulated from the baseshell. The upper end of the pin is rounded and the lead wire 7 emergesthrough an opening at l) which is somewhat reduced in size with respectto the internal bore of the pin. As illustrated in the drawings, moreparticularly in Figs. 3a and 3b, the pin is relatively thin-walled andhas a bore several times larger in diameter than the lead wire threadedthrough it.

In making a welded pin connection embodying my present invention, 1 usea method of welding sometimes known as spot-deposition welding. it isgenerally similar to that described and claimed in my copendingapplication Serial No. 306,828, filed August 28, 1952, entitled LampBase Welding, and assigned to the same assignee as the presentinvention, now Patent 2,708,702--Albrecht. T re preparatory processingof the lamp and the welding itself may be carried out at successivestations of a rotary lamp finishing machine, such as disclosed forinstance in U. S. Patent 1,768,756 Pagan. Such machines in generalcomprise a turret or turntable on the outer periphcry of which the lampsare vertically supported in suitable chucks, and means forintermittently rotating the turret. While the lamps are stationary atthe various stations, the required operations are performed by suitablemechanisms fixed in position around the periphery of the turret andsynchronized to operate during the dwell intervals. The variousoperations now to be described are preferably performed on such amachine.

Figs. 2a to 2d illustrate the sequence of steps in making aweldedconnection such as illustrated in Fig. 3b. The first step involvescutting off the excess length of the lead wire so as to leave arelatively short stub, in general no longer than the diameter of thepin. This may be done in well-known fashion by means of reciprocating2a. A knife-edged cutter 21, moving in the direction of the arrow 22,slides over a cooperating blade 23 and shears off the excess length "7aof the lead, leaving a short stub 7b upstanding through the opening inthe upper end of the pin.

in the next operation, illustrated in Fig. 2b, the stub is bent overinto the position wherein it lies substantially horizontal. Thisoperation may be effected during the rotary movement of the lamp on thefinishing machine turret by means of a wiper 24 whose lower end ispositioned to engage the wire while the lamp is moving in the directionindicated by the arrow 25. The projecting stub is then rolled down onthe edge of the pin, as illustrated at in in Fig. 20. This operation mayalso be accomplished while the lamp is in movement as indicated by thearrow 26, by means of a roller 27, carried on a spring-loaded arm 28 andpositioned to engage the lead wire. The position of the projecting stuband its general configuration after the rolling operation are moreclearly illustrated in Fig. 3a.

The welding operation may be carried out by means of a mechanism such asillustrated in Fig. 2a. The lamp is now stationary at a station of themachine where the shank of the pin is engaged near its lower end by acontact member 29. Positioned immediately above the pin is a massivecylindrical electrode 30 supported in an insulating block 31. Theelectrode may be cylindrical in form with a flat lower surface 32 and ofa diameter considerably greater than that of the pin. It will beappreciated that the term massive, as applied to the electrode, is bycomparison with the size of the pin. The object is to make the heatcapacity of the electrode 3t) much greater than that of the pin, so thatthe heat from the condenser discharge will fuse the lead wire and thetip of the pin without any substantial effect on the electrode itself.Also, the fact that the lower surface 32 of the electrode is flat andconsiderably greater in diameter than the pin, serves to reflect theheat of the electric discharge onto the pin. The electrode block 31 iscarried on the lower end of a rod 33 which is slidably supported in abushing 34. A transverse pin 35 in the upper end of the rod rests on theend of a rocker arm 36 pivoting at 37 and actuated by a connecting rod38 in synchronism with the indexing of the finishing machine turret. itwill be appreciated that connecting rod 38 is synchronized to the turretin such manner as to lower the electrode 31') during the dwell intervalof the lamp at the welding station.

As the electrode 39 is lowered, it contacts the stub 7d of the lead wireand the welded connection then results almost instantaneously from thedischarge of the capacitor 41. The welding current is exponential inwaveform, that is, it has a drooping vol -ampere characteristic andstarts off at a relatively high value, dropping off very quickly to alow value. Due to the rapidity with which the weld is made, the wattageor quantity of electricity required is relatively small. As illustratedschematically, condenser ll is arranged to be discharged by reason ofthe direct connection from the positive side of the condenser to thecontact finger 29 which engages the shank of the pin, and the connectionfrom the negative side of the condenser through rheostat 42 to electrode36). Capacitor 41 may have a value of approximately 5,000 microfaradsand rheostat 42 may be adjustable between zero and 3 ohms. For weldingthe pins of the usual fluorescent lamp which extend above the base shellapproximately one-third of an inch and wherein the lead wire consists of16 mil copper wire, rheostat 42 may be set at approximately 1.5 ohms andcapacitor 41 may be charged to approximately 400 volts at the beginningof the welding cycle.

Capacitor 41 may be recharged in between the welding operations throughany conventional system. For instance as illustrated in the drawing, therecharging means may comprise a voltage step-up transformer 43 and ahalf wave rectifier 44. The rectifier 44 is connected in series with thesecondary winding 45 of the transformer and a pair of relay contacts 46across capacitor 41. Relay contacts 46 are normally closed and may bearranged to open just prior to the discharge of the capacitor in orderto prevent short circuiting the rectifier 44- and transformer secondary4-5 at the time when the weld is made. The primary winding 47 of thetransformer may be energized at terminals 48 from the usual 1l5120 voltcycle supply mains.

At the instant when electrode 30 contacts the bentover stub 7d of thelead wire, conditions are as illustrated in Fig. 3a. Capacitor d1 beginsto discharge immediately with a heavy current, for instance 100 amperesthrough the lead wire. The maximum resistance in the circuit, exclusiveof the control rheostat 42, occurs in the stub 7d of the lead wire andat the point where the stub is pressed against the lip of the opening 19in the end of the pin. By reason of the low thermal mass of the wirestub, it melts almost immediately and part of it is vaporized. Themetallic circuit is thereby broken, but the discharge of the capacitor,which is still charged nearly to its high initial value, continuesthrough the metal vapor. The flat lower surface 32 of massive electrode30 assists in concentrating the heat of the discharge on the end of theelectrode, as indicated at 51 in Fig. 3b. By reason of the exponentialtype of discharge obtained with a capacitor, the heat is developed veryquickly and the lead wire stub and the tip of the pin liquify and dropback from the elec trode more quickly than the electrode is lowered bythe movement of the connecting rod 38. The capacitor is thus practicallyentirely discharged through the metal vapor and the molten metal fusesand closes the end of the pin, as indicated at 52, before the electrodecontacts it again.

It is not necessary to cause the electrode to contact the pin a secondtime after the weld is made, but there is no objection to it. As apractical matter, the height of the pins may vary slightly as a resultof dimensional variations and also as a result of slight misalignment ofthe lamp holders on the finishing machine turret. Accordingly, in orderto prevent the possibility of the electrode failing to contact the pinat all, it is preferable to adjust the mechanism such that the electrodeis lowered sufficiently to rest entirely on even the shortest pin afterthe weld is made. The possibility of missing some of the pins is thusavoided. At, the second contact of the electrode with the pin, there isvery little charge left in the capacitor and any spark that may occur isof very low intensity and has substantially no effect.

As illustrated in Fig. 3b, the weld junction 52 consists solely ofintermingled metal from the lead wire and from the end of the pin. Themajor part of the fused weld metal comes from the end of the pin. Thepin is foreshortened from its original configuration as illustrated indot-dash lines at 5,3, and this feature provides enough metal to closethe hole 19 in the end of the pin. In actual practice, the pin isforeshortened between .015 to .025 inch and this provides enough metalto achieve complete closure of the pin along with a satisfactory weldjunction.

When the Weld junction is made by first bending over the projecting stubof the lead wire as illustrated in Fig. 3a, the weld junction results inan externally smoothly contoured end wall on the pin, but slightlyflattened and somewhat unsymmetrical, as illustrated in Fig. 3b. Inaccordance with a variant of my invention which is illustrated in Fig.4b, I may provide a weld junction which results in a more rounded andsymmetrical end on the pin. To achieve it, the projecting end of thelead wire is cut of? to leave a short projecting stub 71') as previouslydescribed with reference to Fig. 2a. The stub 71) is left in straightupstanding position, that is it is neither bent nor rolled over. It willbe appreciated that in order for the discharge of the capacitor tostart, there must initially be circuit continuity between the lead wireand the pin. Generally, there will be contact somewhere within the boreof the pin between the lead wire and the pin, even though no specialprovision is made to assure the occurrence of such contact. However, asan additional safeguard to insure a positive contact, the base may be totated with respect to the lamp during the basing operation so as tocause the lead '7 to enter the bore of the pin at an angle. This insuresthat a contact connection is present at the point where the lead is bentto enter the bore of the pin, as illustrated at in Fig. 4a.Alternatively, the wire may be kinked before it is threaded through thepin and a contact connection will then be present where the wire pressesagainst the pin wall.

The method followed in making the weld thereafter is generally the sameas what has already been described. The electrode 30 is lowered intoengagement with the end of the lead wire stub 75, and the initialcircuit con tinuity occurs through the lead down to the junction point7e and then back through the shank of the pin to the contact 29. Theprojecting stub 71) is vaporized almost instantaneously, and thedischarge then occurs through the metal vapor from the surface 32 ofelectrode 39 to the tip of the pin 12. It will be appreciated thatfollowing the vaporization of the stub 7b, the current flow is divertedfrom the lead wire to the shank of the pin so that there is no danger ofmelting and burning off the lead within the bore of the pin. Theresulting weld connection is illustrated at 54 in Fig. 4b. Theforeshortening of the pin from its original length, indicated at 53, isabout the same as previously described, but the end of the pin is morerounded and symmetrical. This feature is somewhat advantageous from thepoint of view of appearance and marketability of the product.

It will be appreciated that in view of the fore-shortening of the pinwhich occurs upon the making of a weld junction embodying my invention,it may be desirable to provide initially a somewhat longer pin thanwhere soldered connections are made. The resultant Welded pin will thenbe of the same length as the soldered pins which were formerly used.

While certain specific embodiments of the invention have been shown anddescribed, it will be appreciated that these are intended asillustrative of the invention only. The invention may readily beembodied in pins of a dif ferent size and configuration, and suitablemodifications in the method and in the apparatus for achieving the weldconnection will readily occur to those skilled in the art. The appendedclaims are intended to cover any modifications in the structure andfeatures of the weld junction coming within the true spirit and scope ofthe invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric device including a lead wire and having a base includingan elongated tubular contact pin, said lead wire being threaded throughthe bore of said pin and being welded into the end of said pin in a weldjunction forming an end wall completely closing the end of said pin andconsisting solely of intermingled metals of the lead wire and of the endof said pin and resulting from the foreshortening of said pin, the majorpart of the fused metal in said weld junction consisting of metal fromsaid pin.

2. An electric device including a lead wire and having a base includingan elongated tubular contact pin, said lead wire being threaded throughthe bore of said pin and being welded into the end of said pin in a weldjunction forming an externally smoothly contoured and completely closedend wall for said pin, said junction consisting solely of intermingledmetals of the lead wire and of the end of said pin and resulting fromthe foreshortening of said pin by an electric capacitor discharge onsaid end, the major part of the fused metal in said weld junctionconsisting of metal from said pin.

3. An electric device including a lead wire and having a base includingan elongated tubular contact pin, the pin being thin-Walled and having abore several times larger in diameter than the lead Wire, said lead wirebeing threaded through said pin to its outer end and welded to the pinat said end in a weld junction forming an externally smoothly contouredand completely closed end wall for said pin, said junction consistingsolely of intermingled rnctal of the lead wire and of the pin, said weldjunction consisting in major part of metal obtained from said end of thepin by foreshortening it.

4. An electric device including a lead wire and having a base includingan elongated tubular contact pin, the pin being thin-walled and having abore several times larger in diameter than the lead wire, said lead wirebeing threaded through said pin to its outer end and welded to the pinat said end in a weld junction forming an externally smoothly contouredand completely closed end wall for said pin, said junction consistingsolely of intermingled metal of the lead wire and of the pin, said weldjunction consisting in major part of metal obtained from said end of thepin by foreshortening it as a result of an electric capacitor dischargeon said outer end of the pin, the major part of the fused metal in saidweld junction consisting of metal from said pin.

References Cited in the file of this patent UNITED STATES PATENTS1,685,382 Stuart Sept. 25, 1928 2,136,005 Dixon Nov. 8, 1938 2,200,954Glassberg May 14, 1940 2,325,817 Watrous Aug. 3, 1943

